In additive fabrication processes with high imaging resolution, in some cases 50 micron or better, that utilize a moveable carrier foil for carrying liquid build material, it is required that the carrier foil be free from wrinkling or excessive stretching. In some processes, this is particularly challenging since the carrier foil must be stationary at the current imaging location while being in motion elsewhere in the additive fabrication process to allow for simultaneous imaging and recoating. Any wrinkling or unanticipated stretching of the foil is undesirable in any foil-based additive fabrication process.
Additive fabrication processes that utilize a UV transparent carrier foil are known. For instance, U.S. Pat. No. 6,557,452 to Fudim utilizes a foil to transport liquid build material to an imaging location. The liquid build material is imaged upon reaching the imaging location and becomes solid. The solid adheres to the previously formed layer of the tangible object and the foil is then moved in order to transport additional liquid build material to the imaging location in order to form the next solid layer. This process is repeated in order to build a solid three-dimensional object. Similarly, U.S. Pat. No. 7,467,939 and U.S. Pat. No. 7,731,887 to 3D Systems, Inc. disclose foil based additive fabrication processes. In each of these processes, the foil is held stationary as the liquid build material is imaged.
In a certain additive fabrication process, the liquid build material may be imaged at one location while the foil is in motion at another location. This process, disclosed in WO2010/074566 to TNO, requires that the foil be kept motionless and wrinkle-free at the imaging location while the foil is in motion elsewhere.
In foil-based additive fabrication processes it is important that the foil does not move, wrinkle, or excessively stretch in any direction at the imaging location. This difficulty is further complicated when the system is capable of bi-directional movement.
A mechanism for additive fabrication which allows for wrinkle-free motion of a foil, especially in a system capable of bi-directional motion, would thus be desirable.